Raman spectroscopy using a spatial heterodyne spectrometer: proof of concept

Area of Science:

• Spectroscopy
• Astrophysics
• Instrument Development

Background:

• Current ultraviolet (UV) Raman spectroscopy for space missions faces challenges with large, complex dispersive instruments.
• Achieving high spectral resolution in UV Raman spectroscopy typically requires narrow slits, limiting light throughput.
• Planetary surface analysis requires robust, compact spectrometers compatible with pulsed lasers for background rejection.

Purpose of the Study:

• To develop a small, rugged, high-resolution UV Raman spectrometer suitable for planetary space missions.
• To overcome the limitations of dispersive spectrometers for UV Raman applications in space.
• To demonstrate the capabilities of a spatial heterodyne interferometer-based spectrometer (SHS) for Raman measurements.

Main Methods:

• Utilized a spatial heterodyne interferometer-based spectrometer (SHS) for Raman spectroscopy.
• Employed a heterodyne approach with weak coupling between resolution and throughput, allowing for a compact design and wide slit.
• Demonstrated simultaneous measurement of optical path differences using a detector array, compatible with gated detection for pulsed lasers.

Main Results:

• Successfully measured visible wavelength Raman spectra of liquid and solid materials using the SHS Raman spectrometer.
• Demonstrated the ability to separate anti-Stokes and Stokes Raman bands using two distinct methods.
• Achieved spectral bandpass doubling by utilizing a two-dimensional Fourier transform analysis of interference patterns.

Conclusions:

• The SHS offers a compact, high-resolution alternative for UV Raman spectroscopy, particularly beneficial for space applications.
• The SHS design overcomes throughput limitations associated with traditional dispersive methods, enabling efficient measurements.
• The demonstrated capabilities suggest the SHS is a viable technology for future planetary exploration and remote sensing.